Field of the Invention
The present invention relates to an imaging apparatus and an imaging method.
Background
Apparatuses are known in which light emitted from a light emission part is received by using a photodetector such as a photodiode to thereby recognize the shape and the like of the light emitted from the light emission part. In such an apparatus, when usual light is received, an output voltage from the photodetector is an appropriate one. On the other hand, in a case where strong light represented by sunlight and the like is received, even when reading out a reset level, due to the leakage of charged electric charges, the level of a signal output which is generated from the output signal of the photodetector obtained by calculating the difference from the reset level is decreased, and therefore, a blackening phenomenon in which a black part in an image arises may occur.
In order to prevent the effect of the blackening phenomenon, it has been proposed that, after a plurality of active pixel sensors are reset, when a reset voltage output to an electric signal converted by the photodetector is in a voltage range that is lower than a voltage in a non-signal duration, the reset voltage is replaced by (fixed to) a predetermined voltage value (for example, refer to Japanese Patent No. 3517614).
Here, an example of the blackening phenomenon is described.
FIG. 16 is a view showing an example in which light having a predetermined luminance or more is incident on a photodetector according to the related art. In FIG. 16, an image g901 shows an example in which light is incident on the photodetector that includes 6×6 pixels. Figure g910 shows a case in which light having an appropriate level is incident on the photodetector that includes the 6×6 pixels. Figure g920 shows a case in which light having a saturation level is incident on the photodetector that includes the 6×6 pixels, and weak saturation arises. Figure g930 shows a case in which light having a saturation level is incident on the photodetector that includes the 6×6 pixels, and strong saturation arises.
Graphs g911, g921, and g931 are graphs showing an example of a luminance output with respect to a cross-sectional direction in a cross-section in the A-B direction of the image g901. In the graphs g911, g921, and g931, the horizontal axis represents a position in the cross-sectional direction in the cross-section in the A-B direction of the image g901, and the vertical axis represents the level of the luminance output.
Graphs g912, g922, and g932 are graphs showing an example of a signal output with respect to the cross-sectional direction in the cross-section in the A-B direction of the image g901. In the graphs g912, g922, and g932, the horizontal axis represents a position in the cross-sectional direction in the cross-section in the A-B direction of the image g901, and the vertical axis represents the level of the signal output.
When the luminance of the light incident on the photodetector is appropriate, as shown in the graph g911, the luminance at the third position in the A to B direction is the highest. When the incidence level on the photodetector is appropriate, as shown in the graph g912, the signal output level of the photodetector also represents a result corresponding to the luminance output, and the signal output level at the third position in the A to B direction is the highest.
When the luminance of the light incident on the photodetector is strong to a degree in which weak saturation arises with respect to the output, as shown in the graph g921, the luminance at the second to fourth positions in the A to B direction is saturated. As the luminance output is saturated, as shown in the graph g922, the signal output level of the photodetector at the third position in the A to B direction at which the signal output is the largest in the case of the incident light having an appropriate luminance is substantially zero, that is, a black level, and the signal output level of the photodetector at the adjacent second and fourth positions is also a value different from a real signal output.
When the luminance of the light incident on the photodetector is stronger than that of the graph g921 and is strong to a degree in which strong saturation arises with respect to the output, as shown in the graph g931, the luminance at the first and fifth positions in the A to B direction is saturated. In this case, the luminance of the incident light is too high, and therefore, the level of the luminance output at the second to fourth positions is not appropriate. As the luminance output is saturated, as shown in the graph g932, the signal output level of the photodetector at the first to fifth positions in the A to B direction is substantially zero, that is, a black level.